Understanding Bee Behaviour — IELTS General Training Reading

Understanding Bee Behaviour

A Bee behaviour has always been a source of wonder. Ancient civilisations marvelled at the organisation of the hive and at the way bees seem to act as a single, intelligent colony. For centuries, however, the question of how bees communicated with one another when they found food remained a mystery. The idea that bees might possess a form of language was dismissed by most scientists, and the study of bee communication would eventually revolutionise the whole field of animal behaviour.

B The breakthrough came in the twentieth century, when the Austrian scientist Karl von Frisch began a long series of careful observations. Working with specially designed glass-walled observation hives, he was able to watch what returning forager bees did when they arrived back at the nest. Von Frisch noticed that returning bees performed a series of distinctive movements on the vertical comb. He realised that these 'dances' were not random movements but appeared to convey information to the other bees.

C Von Frisch identified three different kinds of dance. The first, a simple circular movement, seemed to tell the other bees that a food source was nearby. The second, a semicircular or 'sickle' movement, appeared to be used when the food was slightly further away. The third was a more elaborate movement which he called the 'waggle' dance. Each dance seemed to correspond to a different distance, and each was performed with increasing excitement the richer the food source.

D Experimenting further, von Frisch unravelled the mystery of the two simpler dances. These dances, he concluded, told the bees simply that within a short distance of the hive there was a food source worth chasing. The longer and more excitedly the scout danced, the richer the promise of the food source. The scent she carried on her body was a message to the other bees that this particular food was the one they were looking for. The others would then troop out of the hive and fly in spiralling circles, sniffing the wind for the promised food.

E At first von Frisch thought the bees were responding only to the scent of the food. But what did the third dance mean? And if bees were responding only to the scent, how could they also sniff out food hundreds of metres away from the hive, food which was sometimes downwind? On a hunch he started moving the feeding dish further and further away and noticed that the dances of the returning scouts began to change. When he placed the dish over nine metres away, the sickle dance came into play. Once he moved it past thirty-six metres, the scouts began to perform the waggle dance. The measurement of distance was precise: a dish three hundred metres away produced fifteen runs through the pattern in thirty seconds, while at sixty metres the number dropped to eleven.

F Von Frisch noticed something further. When the scout bees came home to tell their sisters about a food source, sometimes they would dance outside on the horizontal entrance platform of the hive, and sometimes on the vertical wall inside. The outside dance was fairly easy to decode: the straight portion of the waggle dance pointed directly towards the food source, so the bees merely had to decode the distance message and fly off in that direction to find their food.

G By studying the dance on the inner wall of the hive, von Frisch discovered a remarkable method the dancer used to tell her sisters the direction of the food in relation to the sun. When inside the hive the dancer cannot see the sun, so she uses gravity instead. The direction of the sun is represented by the top of the hive wall. If she runs straight up, the feeding place is in the same direction as the sun. If, for example, the feeding place is 40 degrees to the left of the sun, the dancer runs 40 degrees to the left of the vertical line. This was the first of von Frisch's remarkable discoveries, and it would go on to revolutionise the study of animal behaviour.